Bosch HFM 5 sensors_airmass.pdf

56 Air-mass meters A BHot-film air-mass meter, Type HFM 5Measurement of air-mass throughflow up to 1000 kg/hQ mU Compact design. Low weight. Rapid response. Low power input. Return-flow detection.ApplicationIn order to comply with the vehicleemission limits demanded by law, it isnecessary to maintain a given air/fuel ratioexactly.This requires sensors which preciselyregister the actual air-mass flow and outputa corresponding electrical signal to theopen and closed-loop control electronics.DesignThe micromechanical sensor element islocated in the plug-in sensor’s flowpassage. This plug-in sensor is suitable forincorporating in the air filter or, using ameasurement venturi, in the air-intakepassages. There are different sizes of measurementventuri available depending uponthe air throughflow. The micromechanicalmeasuring system uses a hybrid circuit,and by evaluating the measuring data isable to detect when return flow takes placeduring air-flow pulsation.Operating principleThe heated sensor element in the air-massmeter dissipates heat to the incoming air.The higher the air flow, the more heat isdissipated. The resulting temperature differentialis a measure for the air mass flowingpast the sensor.An electronic hybrid circuit evaluates thismeasuring data so that the air-flow quantitycan be measured precisely, and itsdirection of flow.Only part of the air-mass flow is registeredby the sensor element. The total air massflowing through the measuring tube isdetermined by means of calibration, knownas the characteristic-curve definition.Technical data / rangeNominal supply voltage U N14 VSupply-voltage range U V8...17 VOutput voltage U A0...5 VInput current I V< 0.1 APermissible vibration acceleration ≤ 150 ms –2Time constant τ 1 63 )≤ 15 msTime constant τ 2 ∆ )≤ 30 msTemperature range –40...+120 °C 3 )Part number 0 280 217 123 0 280 218 019 0 280 217 531 0 280 218 008 0 281 002 421Measuring range Q m 8...370 kg/h 10...480 kg/h 12...640 kg/h 12...850 kg/h 15...1000 kg/hAccuracy 4 ) ≤ 3% ≤ 3% ≤ 3% ≤ 3% ≤ 3%Fitting length L E 22 mm 22 mm 22 mm 16 mm 22 mmFitting length L A 20 mm 20 mm 20 mm 16 mm 20 mmInstallation length L 96 mm 96 mm 130 mm 100 mm 130 mmConnection diam. D 60 mm 70 mm 80 mm 86/84 mm 6 ) 92 mmVenturi ID 50 mm 62 mm 71 mm 78 mm 82 mmPressure drop atnominal air mass 5 )< 20 hPa < 15 hPa < 15 hPa < 15 hPa < 15 hPaTemperature sensor Yes Yes Yes No YesVersion 1 2 3 4 51 ) In case of sudden increase of the air-mass flow from 10 kg · h –1 auf 0,7 Q m nominal, time required to reach63% of the final value of the air-mass signal.2 ) Period of time in case of a throughflow jump of the air mass | ∆ m/m | ≤ 5%.3 ) For a short period up to +130 °C.4 ) |∆Q m/Q m|: The measurement deviation ∆Q m from the exact value, referred to the measured value Q m.5 ) Measured between input and output6) Inflow/outflow endAccessories for connectorPlug housing Contact pins Individual gaskets For conductor cross-section1 928 403 836 1 987 280 103 1 987 280 106 0.5...1 mm 21 987 280 105 1 987 280 107 1.5...2.5 mm 2Note: Each 5-pole plug requires 1 plug housing, 5 contact pins, and 5 individual gaskets.For automotive applications, original AMP crimping tools must be used.ApplicationIn internal-combustion engines, this sensoris used for measuring the air-mass flowso that the injected fuel quantity can beadapted to the presently required power, tothe air pressure, and to the air temperature.Explanation of symbolsQ m Air-mass flow rate∆Q m Absolute accuracy∆Q m /Q m Relative accuracyτ ∆ Time until measuring error is≤ 5%τ 63 Time until measured-value change63%

B A Air-mass meters 57Function diagram with connector-pin assignment.1 Additional temperature sensor ϑ u (not on version 4, Part number 0 280 218 008),2 Supply voltage U V, 3 Signal ground, 4 Reference voltage 5 V, 5 Measurement signal U A.ϑ Temperature-dependence of the resistor, R H Heater resistor, U K Constant voltage12HFM 5 plug-in sensor design.1 Measuring-passage cover, 2 Sensor,3 Mounting plate, 4 Hybrid-circuit cover,5 Hybrid, 6 Plug-in sensor, 7 O-ring,8 Auxiliary temperature sensor.14ϑ uϑ ϑ354U K235ϑϑR H87 6Output voltage U A = f(Q m ) of the air-mass meterPart number 0 280 217 123 0 280 218 019 0 280 217 531 0 280 218 008 0 280 002 421Characteristic curve 1 2 3 4 5Q m /kg/h U A /V U A /V U A /V U A /V U A /V1118 1.4837 1.2390 – – –1110 1.5819 1.3644 1.2695 – –1115 1.7898 1.5241 1.4060 1.3395 1.23151130 2.2739 1.8748 1.7100 1.6251 1.47581160 2.8868 2.3710 2.1563 2.0109 1.83101120 3.6255 2.9998 2.7522 2.5564 2.30741250 4.4727 3.7494 3.5070 3.2655 2.92121370 4.9406 4.1695 3.9393 3.6717 3.28741480 – 4.4578 4.2349 3.9490 3.54611640 – – 4.5669 4.2600 3.84321850 – – – 4.5727 4.14991000 – – – – 4.3312Air-mass meter output voltage.Output voltage UAV51 2 3 4 54321Temperature-dependence R ϑ = f(ϑ) of the temperature sensorTemperature ϑ °C –40 –30 –20 –10 ±0 10 20 30 40Resistance R ϑ kΩ 39.26 22.96 13.85 8.609 5.499 3.604 2.420 1.662 1.166Temperature ϑ °C 50 60 70 80 90 100 110 120 130Resistance R ϑ Ω 835 609 452 340 261 202 159 127 10200200 400 600 800 1000 kg/hAir-mass flow Q mTemperature-resistance diagram of the temperature sensor.40Nominal resistance R ϑ Nom. at 25 °C: 2.00 kΩ ± 5 %kΩ302010R ϑ Nom.Resistance Rϑ0-40-20 ±0 20 40 60 80 100 °CTemperature ϑDimensions overview of the HFM 5.1 Plug-in sensor, 2 Throughflow direction,3 Measurement venturi.23LE1LLAD

172 | BoschPart number 0 281 002 421With ambient-temperature sensor.Technical dataIllustrationMeasuring range { -50 ... 1200 kg/hDimension drawing! ' & ' ! & " 1 Plug-in sensor2 Flow direction3 Measurement tubeAir-mass characteristic curve at ambient temperatureUAV43210–50 0 200 400 600 800 1000 m /kg·h –1AccessoriesPart numberCompact connector 5-pin 1 928 403 836Contact pins for ; 0.5...1.0 mm2; Contents: 100 x 1 928 498 056Contact pins for ; 1.5...2.5 mm2; Contents: 100 x 1 928 498 057Single-wire seals for ; 0.5...1.0 mm2; Contents: 10 x 1 928 300 599Single-wire seals for ; 0.5...1.0 mm2; Contents: 10 x 1 928 300 600Accessories are not included in the scope of delivery of the sensor and are therefore to be ordered separately as required.